WHEELING, W.V. — Doug Marshall wasn’t thrilled with what he heard. Seated at a makeshift desk at St. Matthew’s Episcopal Church, the organ maker ascended the keys of a plastic keyboard he’d propped on a pew to his side. A laptop glowed before him. But the real object of his attention stood by the altar: Opus 10, his newly minted digital organ with four keyboards, a gleaming shell of burnished wood, and the full sonic force, filigree, and thunder of 9,000 pipes — all without a pipe to be found.